Chemical and Energy Recovery Process
A thermodynamically efficient use of fuel, the cogeneration process is more efficient because energy in steam is used productively. At a typical electric generating plant, steam is used only once to make more electricity. The steam must then be condensed back into water, thereby wasting the remaining energy in the steam. At Glatfelter’s integrated facilities in the U.S., steam is used first to manufacture electricity, and is then used to make pulp and paper.
At our large integrated mills in the U.S., most of the alternative energy Glatfelter uses comes from the same trees harvested to make paper. Half of the biomass in a tree is cellulose fiber, which is used to make paper. The other half is lignin, a glue-like material that holds the cellulose fibers together to make a tree stand up straight. Lignin cannot be used to make the high-quality papers manufactured by Glatfelter, so it must be separated from the cellulose during the pulping process.
Instead of making paper out of lignin, it is burned in a special recovery boiler to recover the cooking chemicals used in the pulping process as well as the biomass energy contained in the lignin. Overall, the recovery system is an efficient recycling process.
At both Spring Grove and Chillicothe, sludge, wood knots, saw dust and other wood wastes are also capable of being burned in conventional power boilers. The Chillicothe mill also has the ability to burn fuel derived from used tires.
On a typical day, over 1900 megawatt-hours of electricity are made at both Chillicothe and Spring Grove. About 50 percent of this electricity comes from renewable energy sources, primarily biomass, with the remainder coming from natural gas. At Spring Grove, more electricity is made than we can use and the remainder is sold to the local utility.
At our non-integrated paper mill in Gernsbach, Germany, two water turbines generate electric power that is sold to the adjacent electric grid. We are currently working with the nearby city of Gaggenau to add two additional water turbines that will increase the capacity to generate sustainable energy.
Many states, including Pennsylvania, have passed legislation mandating that retail electric providers obtain a certain percentage of electricity from renewable sources. Every megawatt-hour of electricity generated from renewable fuels is assigned one Renewable Energy Credit or REC. These RECs are sold to retail electric providers to help them meet their REC requirements.
What is a CFB Boiler?
Circulating Fluidized Bed Boiler (CFB) is a power boiler with a special design where solid fuel is fed to the fluidized boiler bed through which combustion air is continuously forced. Bed ash is separated by size in a cyclone and larger particles are returned to the fluidized bed. The benefits include the flexibility to burn multiple fuels; low emissions; and beneficial use of ash. Glatfelter operates a CFB at its Spring Grove, PA facility.
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